HUNDREDS OF PREGNANT WOMEN IN THE U.S. HAVE ZIKA VIRUS

At least 279 pregnant women in the U.S. and its territories have been infected with the Zika virus, more than double the number

most recently reported, federal health officials said Friday.

The higher number reflects changes in reporting criteria rather than a sudden spike in U.S. Zika cases. It includes all pregnant women in the U.S. and its territories who have tested positive for Zika infection, whether or not they developed symptoms or complications in their pregnancies, the Centers for Disease Control and Prevention said in a report Friday. The previous numbers included only pregnant women who had Zika symptoms or pregnancy complications, the CDC said.

The new numbers come from two registries set up by the agency in February to gain a fuller picture of the effects of Zika on pregnant women and their unborn children, the CDC said. It has registered and is monitoring 157 pregnant women in U.S. states and the District of Columbia, and 122 pregnant women in U.S. territories—mostly Puerto Rico—who were infected with Zika through May 12.

The surveillance system it was relying on previously had recorded 113 pregnant women as of May 11, including 48 in U.S. states and D.C., and 65 in U.S. territories.

The CDC has said that the vast majority of people infected with Zika don’t develop symptoms. While the agency has determined that Zika can cause a condition known as microcephaly and other severe birth defects in fetuses, it is not known how often that occurs when a pregnant woman is infected with Zika. Studies have shown that birth defects may develop whether or not an infected pregnant woman develops symptoms of Zika.